Field
Implementations described herein generally relate to deposition of etch stop films. More specifically, implementations described herein generally relate to AlN deposition in back end of line (BEOL) processing.
Description of the Related Art
With continued device scaling, interconnect RC delay continues to escalate. Among several efforts being made to address this challenge, one is to lower the capacitance contributed by the dielectric diffusion barrier layer. Lowering the capacitance can be achieved by either lowering the dielectric constant or physically thinning down the barrier although there are trade-offs with each approach.
Lower k barriers are generally less dense materials which limit their ability to function as robust barrier to oxidation, moisture penetration and Cu diffusion. On the other hand, physically thinning down the barrier is constrained by the ability of the thin layer to serve as an effective etch stop layer, especially given micro-loading and non-uniformity of dry etch processes. In this context, traditional SiCN based or SiOC based barrier/etch stop layers have reached their scaling limit.
Bilayers of alternative materials with much higher dry/etch etch selectivity and SiCN/SiOC have been considered in order to continue scaling effective capacitance while affording adequate etch stop protection. From this perspective, aluminum nitride (AlN) is an attractive material. AlN has excellent selectivity to ultra low k (ULK) etch, good insulating properties and reasonable dielectric constant of 8-9. Traditionally, AlN is deposited by CVD or ALD methods. These methods tend to leave undesired organic ligands in the film resulting in inferior material quality. Plasma enhanced ALD (PEALD) can yield superior film quality by employing plasma treatment steps; but plasma treatments can damage underlying ULK.
Therefore, a there is a need for alternative methods of depositing AlN layers for BEOL processes.